Japanese unexamined patent application publication No. JP-A-2004-323131 describes a related art sheet discharging device. The related art sheet discharging device is configured such that sheets discharged from a main body to a sheet discharging tray can be stacked appropriately in order of discharge. However, in a case where the main body is a part of an image forming apparatus which forms an image on the sheet, for example, by electro-photography, the sheet is subjected to a thermal fixing process before being discharged, and thus the discharged sheet is often curled due to the influence of heat generated in the thermal fixing process. Accordingly, the related art sheet discharging device has a disadvantage in that it is often difficult to stack such curled sheets on one another orderly in the sheet discharging tray.
FIG. 10 shows a related art sheet discharging device 22. Each conveyed sheet 7 is discharged from a discharge port 34 to a sheet discharging tray 16 by a discharge roller (not shown). Two pressing units 66 are provided in the discharge port 34 so that the pressing units 66 press the sheet 7 discharged to the sheet discharging tray 16. The two pressing units 66 are provided substantially at opposite end portions of the discharge port 34, respectively, in the width direction of the sheet. In each pressing unit 66, a pressing member 68 is provided 66 so that the pressing member 68 can rotate around a pivot 76. The pressing members 68 press substantially opposite end portions in the width direction of the sheet 7 discharged from the discharge port 34 to the sheet discharging tray 16. Since the sheet 7 is apt to be curled at its opposite edge portions, the pressing members 66 are disposed at positions corresponding to the opposite edge portions of the sheet that is conveyed, respectively. Accordingly, the curl of the sheet 7 is corrected.
However, the related art sheet discharging device still has some disadvantages. For example, each of the pressing members 68 has one end connected to the pivot 76 so that the pressing member 68 can rotate around the pivot 76. The uprise angle and weight of each pressing member 68 are set to keep balance between curl correction and conveyance resistance, so that the pressing member 68 presses each discharged sheet 7 with its own weight. However, if an extensively curled sheet 7 is discharged, the pressing members 68 cannot correct opposite edge portions of the sheet 7 because the pressing members 68 rotate counterclockwise and the weight of the pressing member 68 is not enough to correct the curl. As a result, the leading end portion of the currently discharged sheet 7 interferes with and presses against a trailing end of a previously discharged sheet 7 to thereby disorder the sheets 7 stacked in the sheet discharging tray 16.